A viscoelastic constitutive relation for the rate-dependent mechanical behavior of rubber-like elastomers based on thermodynamic theory

Because of large deformation and viscoelastic properties of rubber-like elastomers, it is very challenging to establish its rate-dependent constitutive relation. Based on the basic theory of thermodynamics, the energy dissipation rate of the materials is derived in this paper. Then, a viscoelastic constitutive relation suitable for describing the rate-dependent behavior of rubber-like elastomers is proposed based on the viscoelastic theory and energy dissipation rate. In order to explain the application of constitutive relation, the constitutive equation is simplified according to the deformation characteristics and boundary conditions of rubber-like elastomers under working conditions, and the simplified one- or two-dimensional constitutive forms are obtained. The existing classical data is fitted and analyzed through the simplified form of the model, and found that the new model has the ability to describe the stress-strain relationship of the materials under common deformation modes. Meanwhile, through comparative analysis found that the overall prediction accuracy of the new model is better than that of some commonly used models. Finally, the newly proposed constitutive relation is used to predict the nonlinear mechanical behavior of three kinds of rubber-like elastomers at different strain rates, and the validity and universality of the constitutive relation are verified through comparative analyses. (C) 2019 The Authors. Published by Elsevier Ltd.